Powder coating compositions for use in painting are extremely desirable. Such coating compositions greatly reduce and can even eliminate organic solvents used in liquid paints. When powder coating compositions are cured by heating, little, if any, volatile material is given off to the surrounding environment. This is a significant advantage over liquid paints in which organic solvent is volatilized into the atmosphere when the paint is cured by heating.
Powder coating compositions formulated with a polyester polymer are especially useful for their corrosion resistance and exterior durability. Powder coating compositions including a carboxylic acid-functional polyester and triglycidyl isocyanurate (TGIC) as a curing agent are common. Although these powder coating compositions give useful coatings with good properties, they are expensive to formulate because of the cost of the TGIC. Also, TGIC presents the formulation with a toxicity problem and requires relatively high cure temperatures of from about 360.degree. Fahrenheit (F.) to about 400.degree. F.